So we got past the looooooong Jan pay-day and I am able to resume by pre-summer kit out...

Having been spurred into action by the thread about plotters/sonar on the SIB forum and having reviewed a number of options I have purchased a Garmin Echomap 45dv CHIRP...

However, I seem to be getting different advice from different places about which transducer to opt for being that this device has CHIRP

The options are:

GT21 - deep salt water; only does down vu on CHIRP (not traditional sonar) (1000+ ft)
GT22 - does both traditional and down vu on CHIRP but classified for fresh water (or some say shallow salt water) (200-500 ft)
GT23 - does both traditional and down vu on CHIRP to decent depth (1000+ ft)

The GT23 is obviously the best option, but retailing at £270 that's more than double what the other two cost and I'm trying to avoid that.

So, being left with the 21 and 22 and knowing that this will only ever be used on a SIB no more than about 3 miles from land... which is the better option?

I'm assuming the 21, but what will I lose?

I guess I don't have a great enough understanding of the different modes of operation to make the most informed decision.

So all are OK for CHIRP... the 8 being cheapest doesn't have DownVu and the only difference for the £120 extra between 22 & 23 seems to be depth with the 23 approx doubling the depth ability from the 22's 800ft Trad/500ft DownVu to 1800ft/1000ft.

There seems to be no mention that any are any more or less suitable for fresh/salt waters.

So for a SIB the 22 seems the optimum??

BTW not sure where the 21 fits in as it doesn't come up on the Garmin UK site but looking elsewhere seems to be near identical specs to the 23 with a slightly lesser traditional range but the same on DownVu??

Which left me thinking, is this simply because freshwater fishermen are more likely to be in shallower water OR is the transducer/frequencies optimised for the density of fresh water as opposed to salt water?

If all things are equal I agree, the 22 might make more sense than the 21 for a SIB - but a smarter man than me will probably need to guide me that last decision...

On my Dragonfly 7 I use the sonar as much as the downvision - often both together on the screen.

Do you need the 1000'+ capability?

As the 22 blurb makes a thing of it being perfect for freshwater I'd want an answer from Garmin themselves as to whether it's suitable for salt water before buying one. I think I'd be surprised if it isn't but better safe than sorry!

I see on the spec for my Garmin 45DV/Transducer combo the saltwater depth range is given (by Garmin) as about half that for freshwater so my guess is that all transducers are suited to either but the depth specs might be about half max stated when in saltwater because it's likely the spec max is given in freshwater.

In buying the CHIRP version of the 45DV you've exposed yourself to greater expense with the choice of CHIRP transducers... boating boy's toys strike again!

The most basic question you forgot to mention is what you intend to use it for.

If you never intend fishing or diving in deep water why spend money on a more detailed deep water transducer. Most of the U.K. Is shallow.

If you intend to dive and need to search for fine detail with a narrow beam then that's what you should look for. If searching for fish then often a wider beam to pick up fish to the side is handy.

I've had transducers for deep water fishing where we target fish in 500m+ with large electric reels. The difference between the likes of airmar tm260 and the $1100 cheaper standard transducer were not noticeable on my bigger high res screen. I ended up selling the tm260 (for a Lowrance).

My advice would be to save your money and go with the cheapest and make sure you find the best place to fit.